Electric system



1955 K. J. GERMESHAUSEN 2,700,121

ELECTRIC SYSTEM Filed March 3, 1947 I INVENTOR. xsuucm J. eeauzsmuszn BY e r ATTORNEY United States Patent ELECTRIC SYSTEM Kenneth .l. Germeshausen, Newton Center, Mass.

Application March 3, 1947, Serial No. 732,114

6 Qlaims. (Cl. 315-180) The present invention, though having fields of more general usefulness in electric systems, is particularly related to systems in which a flash condenser is discharged through the gaseous medium of a gaseous-discharge device for such purposes as to produce a single flash or a repetition of flashes in flash-photography and stroboscopic work.

The most efiicient flash-producers of the above-described character in use today embody flashlamps, commonly called flashtubes, provided with not only an anode electrode and a cathode electrode between which to send the flash-producing current through the gaseous medium, but also a high-voltage starting, control or trigger electrode. The necessity for employing the trigger electrode introduces complexities and increases the size of the gaseous-discharge device, but the proposals that have heretofore been made for eliminating it have not been satisfactory.

An object of the present invention, therefore, is to provide a new and improved electric system of the abovedescribed character embodying a two electrode gaseousdischarge device.

Another object is to provide a new and improved flashproducing system of the above-described character embodying a flash device unprovided with a starting or control electrode.

An additional object is to provide a new and improved condenser-discharge system embodying a gaseous-discharge device isolated by a spark gap from the potential of the flash condenser except at the instant of the discharge.

A- further object is to provide a new and improved condenser-discharge circuit of the above-described character having a two-electrode triggering spark-gap gaseous-discharge device in series with the gaseous-discharge tube.

Another object is to provide a new and improved electric system of the above-described character in which the discharge of a condenser through a two-electrode gaseous-discharge device may be under the control of a twoelectrode spark gap.

Another object still is to reduce the expense of systems of the above-described character.

Other and further objects will be explained hereinafter, and will be particularly pointed out in the appended claims.

With the above ends in view, a feature of the invention resides in a series-triggering arrangement for producing the flash of a two-electrode flash device through the medium of a voltage provided by a saturable core transformer disposed in a specific part of the condenser-discharge circuit.

The invention will now be more fully explained in connection with the accompanying drawings, the single figure of which is a diagrammatic view of circuits and apparatus arranged and constructed according to a preferred embodiment of the invention.

A main-discharge flash condenser or capacitor 11, shown charged from a direct-current source, illustrated as a battery 10, through a current-limiting charging impedance 12, is shown series-connected in a discharge circuit to the anode electrode 7 and the cathode electrode 9 of a normally non-conducting two-electrode gaseous-discharge device, such as a space-discharge flashtube or flashlamp 18. The condenser 11 may be charged to a voltage of from 200 to 2000 volts. The flashes are produced by discharging the condenser 11, after it has become charged, through the discharge circuit and through the gaseous medium of the lamp 18, between the anode 7 and the cathode 9.

Because of the dielectric properties of the normally deionized air in the space between the spark-gap electrodes 104 and 106, the direct-current source will charge the condenser 11 through the impedance 12 without any of its energy traversing that space. A difference of potential will therefore be established between the spark-gap electrodes 104 and 106 during the charging of the condenser 11 before each flash. The impedance 12 should be designed sufliciently large so that, after the creation of the spark between the electrodes 104 and 106, further current flow between them will be prevented until after the air of the spark gap shall have again become deionized. The impedance 12 should, however, be small enough to permit of the condenser 11 becoming recharged with energy from the direct-current source 10 in time for the next flash.

The secondary winding of a triggering transformer 14 is shown in the condenser-discharge circuit, in series with the two electrodes 104 and 106 of the spark gap. The electrode 104 is shown connected to the anode 7 and the electrode 106 to a terminal 19 connecting one side of the condenser 11 to the current-limiting impedance 12. A high-voltage pulse is designed to be impressed momentarily upon the secondary winding 15, at a suitable time, in order to ionize the air between the spark-gap electrodes 104 and 106 and to break down or ionize the gas in the lamp 18. As an illustration, a high-voltage low-energy spark may jump across between the electrodes 104 and 106, essentially connecting one terminal of the secondary winding 15 of the transformer 14 to one terminal of the condenser 11. Under these conditions, the voltage across the lamp 18 becomes the sum of the voltage on the condenser 11 and the voltage developed across the secondary winding 15 of the transformer 14 a resultant voltage high enough to cause the lamp 18 to ionize, thereby rendering it conducting. Upon the lamp 18 becoming thus conducting, the condenser 11 will suddenly discharge therethrough, between the anode 7 and the cathode 9.

The necessarily high-peak-discharge currents are thus effectively controlled by a simple inexpensive triggering two-electrode spark gap. As the additional high-voltage trigger electrode that is customarily employed with gaseous-discharge flash-lamps is unnecessary according to the present invention, the connections become simplified,

) and it becomes possible to employ a gaseous-discharge device 18 of smaller size.

The momentary voltage pulse for triggering the spark gap may be induced in the secondary winding 15 by supplying a corresponding voltage pulse for energizing the primary winding 13 of the transformer 14. This may be efiected in any desired way, as by discharging a small trip condenser 40 through the primary winding 13, in series with a normally non-conducting trigger tube 1, by way of lead wires and 31. Because of the normally non-conducting character of the trigger tube 1, it provides a normally open switching device. The impedance of the lead wires 30 and 31, which may be fairly long, should not be too great compared to the impedance of the primary winding 13. The condenser may be of the order of 0.1 microfarad, compared to the order of 10 microfarads for the condenser 11.

The condenser 40 may be charged from any desired direct-current source, such as a bleeder resistor. The bleeder resistor is shown comprising two resistor sections 81 and 82 connected in series across the battery 10 to constitute a voltage divider for adjusting the voltage on the condenser 40. The free terminal of the resistor 81 is connected to the terminal 19, at one side of the condenser 11, and the free terminal of the resistor 82 is connected to the other side of the condenser 11.

The trigger tube 1 should be of a type capable of passing high-peak currents. It may, for example, be of the normally non-conducting cold-cathode gaseous-discharge type illustrated and described in Letters Patents 2,185,189, 2,201,166 and 2,201,167, issued January 2 and May 21, 1940. It may comprise an evacuated glass envelope filled with a suitable gas, such as neon, or any of the other noble gases, such as. argon or helium. The tube 1 is shown containing several electrodes, namely, a solid cold cathode 2, an anode or plate 5, and one or more grids 4. As explained in the said Letters Patent, the source of the electrons is a bright cathode spot on the surface of the cathode 2. The moment of discharge of the condenser 40 through the primary winding 13 is controlled by the potential on the grid 4 of the trigger tube 1. An impedance 24, illustrated as a resistor is shown connected between the cathode 2 and the grid 4, in parallel with terminals 20;

When it is desired to trigger the flashes of the lamp 18, a potential is applied to the control-grid electrode 4 through the terminals 20. This results in closing the said normally open switching device, and triggers the tube 1 to enable the trip condenser 40 to discharge therethrough and through the primary winding 13. The voltage and the power necessary to effect this result depend upon the design or" the particular tube 1 employed.

The polarity of the voltage pulse impressed upon the secondary winding 15 is preferably in the same sense as the sense of the voltage across the condenser 11. This polarity being therefore additive with respect to the charge on the condenser 11, it will aid the voltage across this condenser 11. This will reduce the magnitude of the voltage required to be supplied by the transformer 14 to tire the lamp 18.

A high impedance 23, shunted across the fiashlamp 13, insures that there shall be no voltage across the lamp 18 until the spark gap is triggered. The impedance 23 may embody both resistance and inductance. This impedance, which may be on the order of a. megohm, is low compared to the leakage resistance across the lamp 18 when it is non-conducting, but high compared to the impedance of the lamp 18 when it is ionized.

it is desirable to have the lamp dimensions and the gas pressure such that the break-down voltage of the fiashtube 18 shall be appreciably greater than the voltage to which the discharge condenser 11 is charged, say, several times as great. It has been found that the lamp 1% then converts a greater proportion of the energy in the condenser 11 into useful light.

Since the secondary winding 15 of the transformer 14 is series-connected in the condenser-discharge circuit, it is desirable, in order to attain high efiiciency and a discharge time that shall not be too long, that its impedance be low with respect to the impedance of the lamp 18 at the time of discharge of the condenser 11. For a reasonable discharge current in the tube 1, on the other hand, it is desirable that the impedance of the primary winding 13 be reasonably high at the time that the triggering impulse is applied to the primary winding 13 and prior to the discharge of the condenser 11.

With a primary winding the effective impedance of which is high at the time of the discharge of the condenser 40, moreover, it is possible to arrange that the impedance of the lead wires 30 and 31 to the transformer primary winding 13, which may be fairly long, shall not be too great compared to the impedance of this primary winding 13. The required low impedance of the secondary winding 15, at the time of discharge of the condenser 11, and the required high impedance of the primary winding 13, at the time that the triggering impulse is applied to the primary winding 13, prior to the discharge of the condenser 11, may be attained by providing the transformer 14 with an iron core that saturates at the time when the main condenser 11 discharges through the transformer in response to the production of the triggering voltage across the secondary winding 15. It is because of the saturable character of the core of the transformer 14 that a low impedance is offered to the discharge of the condenser 11 through the discharge circuit including the gaseous-discharge device 18. The permissible saturated inductance of the secondary winding 15 of the transformer 14 may be computed from the well-known equations governing the transient behavior of a series-discharge circuit of resistance, inductance and capacitance.

The impedance of a typical fiashlamp 18, for example, 30 centimeters long and 4 millimeters inside diameter, and filled with xenon at centimeters pressure of mercury, may be 3 or 4 ohms. A typical condenser 11 may be of 10 microfarads capacity. The transient .in the series-condenser-discharge circuit comprising the condenser 11, the. secondary winding 15 and the lamp 18 will depend on the relative proportions of the resistance, inductance and capacitance.

The saturated inductance of the secondary winding 15 of the transformer 14 may be as great as 40 microhenries without seriously affecting the duration of the flash or the peak current in the condenser-discharge circuit. If the resistive component of the impedance of the secondary winding 15 is low compared to 4 ohms, the efiiciency will still be good, and the operation will be comparable to the operation that takes place without the transformer 1.4. Under the above conditions, the operation will be satisfactory so long as mostpractical cases, it is permissible to tolerate even the relation A typical transformer 14 may have a closed iron core of 0.094 square inch cross-section and 4 inches effective length, and may be constituted of a good grade of thin silicon-steel laminations. On this core may be wound a secondary Winding 15 of 50 turns and a primary wind.- iug 13 of 5 turns. When the iron core is saturated, the inductance of the primary winding 13 may be of the order of 0.20 microhenry and that of the secondary winding 15 of the order of 20 microhenries. The saturated inductance of 20 microhenries for the secondary winding 15 is well below the value of 40 microhenries before referredv to. When the iron core is not saturated, the inductance may be times as great, corresponding to a primary-winding inductance of 20 microhenries. Since ordinary cable has an inductance on the order of 0.2 microhenry per foot, this value is large enough so as not to introduce troubles due to the impedance of the lead wires 30 and 31.

The impedance across which the excess voltage to the lamp 18 is delivered need not be constituted, however, of the secondary winding 15 of the transformer 14. As explained in application, Serial No. 679,983, filed June 28, 1946, it may be in the form of a saturable inductor reactor, not shown, comprising an iron core. In either event, the voltage impressed upon the saturable-core reactor is of magnitude such that, when added to the charge upon the condenser 11, it will exceed the magnitude of the break-down voltage of the fiashtube 18.

The spark gap, moreover, serves the further important function of. isolating the flashtube 18 from the high directcurrent potentials of the condenser 11 and the spark gap, except at the instant of flash. As these highpotential elements may be completely enclosed at some distance from the lamp 18, the operator may be fully protected from these high potentials, except at the moment of discharge. The enclosure, not shown, for these high-potential elements, may be rendered soundproof, in order to render the operation of the spark gap inaudible.

Modifications will occur to persons skilled in the art, and all such are considered to fall within the spirit and scope of the invention, as defined in the appended claims.

What is claimed is:

1. An electric system having, in combination, a gaseons-discharge device, a condenser, means for charging the condenser, a two-electrode spark gap, a saturablecore inductor, a discharge circuit for the condenser including the gaseous-discharge device, the inductor and the spark gap connected in series, and means for impressing a voltage upon the inductor of magnitude such that, when added to the charge on the condenser, it will produce a voltage of magnitude sufiicient to cause the break-down of both the spark gap and the gaseous discharge device, thereby to enable the condenser to discharge through the discharge circuit.

2. An electric system having, in combination, a gaseous-discharge device, a condenser, means for charging the condenser, a two-electrode spark gap, a saturablecore transformer, adischarge circuit for the condenser including the gaseous-discharge device, the transformer andthe spark gap. connected in series, and means: for impressing-a voltage upon the transformer-of magnitude such that, when added to the charge on the condenser, it will produce a voltage of magnitude sufiicient to cause the break-down of both the spark gap and the gaseousdischarge device, thereby to enable the condenser to discharge through the discharge circuit.

3. An electric system having, in combination, a gaseous-discharge device, a condenser, means for charging the condenser, a two-electrode spark gap, a discharge circuit for the condenser including the gaseous-discharge device and the spark gap, and means for impressing a voltage upon the discharge circuit in the same sense as the sense of the voltage on the condenser and of magnitude such that, when added to the charge on the condenser, it Will produce a voltage of magnitude suflicient to cause the break-down of the spark gap, thereby to enable the condenser to discharge through the discharge circuit.

4. An electric system having, in combination, a gaseous-discharge device, a condenser, means for charging the condenser, a two-electrode spark gap, a saturablecore inductor, a triggering device, a discharge circuit for the condenser including the gaseous-discharge device, the inductor and the spark gap connected in series, and means for triggering the triggering device to impress a voltage on the inductor of magnitude such that, when added to the charge on the condenser, it will produce a voltage of magnitude sufficient to cause the breakdown of both the spark gap and the gaseous-discharge device, thereby to enable the condenser to discharge through the discharge circuit.

5. An electric system having, in combination, a gaseons-discharge device, a condenser, means for charging the condenser, a two-electrode spark gap, an inductor, a discharge circuit for the condenser including the gaseous-discharge device, the inductor and the spark gap connected in series, and means comprising a grid controlled rectifier for impressing a voltage on the inductor of magnitude such that, when added to the charge on the condenser, it will produce a voltage of magnitude sufiicient to cause the break-down of the spark gap, thereby to enable the condenser to discharge through the discharge circuit.

6. A flash-producing system having, in combination, a gaseous-discharge flash device, a condenser, means for charging the condenser, a two-electrode spark gap, a saturable-core transformer, a triggering device, a discharge circuit for the condenser including the flash device, the transformer, the spark gap and the triggering device, and means for triggering the triggering device to impress a voltage on the inductor of magnitude such that, when added to the charge on the condenser, it will produce a voltage of magnitude suflicient to cause the breakdown of both the spark gap and the flash device, thereby to enable the condenser to discharge through the discharge circuit in order to produce a flash.

References Cited in the file of this patent UNITED STATES PATENTS 1,745,830 Bethenod Feb. 4, 1930 2,096,865 Swart Oct. 26, 1937 2,142,837 Edwards Jan. 3, 1939 2,178,423 Inman Oct. 31, 1939 2,186,013 Edgerton Jan. 9, 1940 2,236,195 McKesson Mar. 25, 1941 2,269,338 Edgerton Jan. 6, 1942 2,326,597 Abernathy Aug. 10, 1943 2,375,130 Perrin May 1, 1945 2,391,611 Back Dec. 25, 1945 2,411,898 Schelleng Dec. 3, 1946 2,416,718 Shockley Mar. 4, 1947 2,431,952 Maxwell Dec. 2, 1947 2,517,031 Rochester Aug. 1, 1950 FOREIGN PATENTS 868,105 France Sept. 15, 1941 

